1. Field of the Invention
The present invention relates to a method of forming a mask pattern suitable for forming a fine thin film pattern, a method of forming a thin film pattern and a method of forming an MR element using the mask pattern.
2. Description of the Related Art
Conventionally, various thin film patterns are used in many ways in the electronic and magnetic devices such as a thin film magnetic head and a semiconductor device formed through a thin-film formation process. Generally, a dry etching process is used to form such thin film patterns, and a mask pattern is necessary in this process. Here, a thin film is formed at first to cover the whole surface of a substrate, then a photoresist pattern with a desired pattern shape is formed on the thin film by photolithography, etc. Subsequently, a dry etching process such as ion milling is applied to the thin film using the photoresist pattern as a mask, thereby a thin film pattern with a desired configuration is formed. Such formation method is employed, for example, in fabrication of a thin film magnetic head including a magnetoresistive (MR) element formed by stacking a magnetic thin film and so on (for example, refer to Japanese Patent Publication No. 2006-260653; Japanese Patent Publication No. 2006-302486; Japanese Patent Publication No. 2006-073088; and Japanese Patent Publication No. 2007-184020), or in fabrication of a wiring pattern of a semiconductor device constituted from a conductive thin film (for example, refer to Japanese Patent Publication No. H05-152294). Thus, to obtain higher formation accuracy in the formation of the thin film pattern including the above-mentioned dry etching process, a mask pattern with high precision is necessary.
However, when a photoresist pattern is employed as a mask pattern as mentioned above, resolution and precision available are limited. It is because the photoresist pattern is easily deformed because it may be shrunk or its corner may be rounded with a thermal influence applied in the dry etching process and physical displacement such as difference in dimensions from its original one is liable to occur. Accordingly, it is difficult to form a fine mask pattern using a photoresist material, and in particular, it is very difficult to form a fine isolated mask pattern. For this reason, it is desirable to use a mask made of an inorganic material.
Meanwhile, methods of forming a magnetic pole of a magnetic write head, which is made of an inorganic material, are proposed (for example, refer to Japanese Patent Publication No. H10-116402 and Japanese Patent Publication No. 2003-131386). Those methods are implemented by what is called a frame plating process.